It is now well accepted that the immune, hematopoietic and skeletal systems have major interactions. Osteoclasts, the cells that resorb bone, are important cellular mediators of skeletal homeostasis and are derived from hematopoietic precursors that also give rise to immune cells. In addition, numerous cytokines, which were first shown to regulate immune cell function, are now known to regulate bone cells and influence skeletal health. Conversely, cells in the osteoblast lineage and their cytokines are critical for the development of the hematopoietic stem cell niche and the normal development of the hematopoietic and immune cell lineages. Up until recently, scientists involved in immune or bone cell research rarely interacted in a significant way because each discipline developed independently and, for the most part, has remained separate. The fundamental hypothesis of the organizers of this conference is that progress in the field of osteoimmunology, which is the study of the interactions of bone, hematopoietic and immune cells in health and disease, will be delayed unless better communication is established between bone biologists, hematologist and immunologists. The goal of The Fifth International Conference on Osteoimmunology: Interactions of the Immune and Skeletal Systems is to bring together scientists from these fields in a setting that will facilitate, interactions, new collaborations and hasten progress towards understanding the interconnections of the immune, hematopoietic and skeletal system. Our four previous meetings were extremely well attended and highly successful. 115- 150 participants from all over the world attended each meeting.